A Schottky diode takes advantage of the metal-semiconductor junction, which provides a Schottky barrier and is created between a metal layer and a doped semiconductor layer. For a Schottky diode with an N-type semiconductor layer, the metal layer acts as the anode, and the N-type semiconductor layer acts as the cathode. In general, the Schottky diode acts like a traditional p-n diode by readily passing current in the forward-biased direction and blocking current in the reverse-biased direction. The Schottky barrier provided at the metal-semiconductor junction provides two unique advantages over p-n diodes. First, the Schottky barrier is associated with a lower barrier height, which correlates to lower forward voltage drops. As such, a smaller forward voltage is required to turn on the device and allow current to flow in a forward-biased direction. Second, the Schottky barrier generally has less capacitance than a comparable p-n diode. The lower capacitance translates to higher switching speeds than p-n diodes. Schottky diodes are majority carrier devices and do not exhibit minority carrier behavior which results in switching losses.
Unfortunately, Schottky diodes have traditionally suffered from relatively low reverse-biased voltage ratings and high reverse-biased leakage currents. In recent years, Cree, Inc. of Durham, N.C., has introduced a series of Schottky diodes that are formed from silicon carbide substrates and epitaxial layers. These devices have and continue to advance the state of the-art by increasing the reverse-biased voltage ratings, lowering reverse-biased leakage currents, and increasing forward-biased current handling. However, there remains a need to further improve Schottky device performance as well as reduce the cost of these devices.